Police are treating an attack by loyalists on a police officer in Belfast on Monday night as attempted murder.

A gang of 15 men tossed a petrol bomb into his unmarked vehicle after surrounding and smashing it outside the offices of Alliance Party MP Naomi Long.

It was the worst incident in another night of sporadic violence in parts of east and south Belfast involving loyalists who took to the streets again in protest against a decision by Belfast City Council to restrict the flying of the Union flag at Belfast City Hall.

PSNI Assistant Chief Constable George Hamilton said the officer was lucky to escape with his life outside the MP's office on the Newtownards Road. He said: "This was a planned attempt to kill a police officer which also put the lives of the public in danger and it is fortunate there were no injuries." Officers were also attacked with petrol bombs in south Belfast close to the M1.

More talks are planned on Tuesday between Peter Robinson, the Northern Ireland First Minister and leader of the Democratic Unionist Party, with Mike Nesbitt, leader of the Ulster Unionist Party, to try to agree some sort of political strategy to ease tensions and end the violence. It follows a meeting between the pair in Belfast on Monday.

They have been heavily criticised by nationalist representatives over their leadership since the trouble flared a week ago. The trouble followed a council decision to limit the flying of the Union flag to designated days. Ms Long's Alliance Party has been blamed by loyalists for supporting the nationalist SDLP and Sinn Fein in pushing through the vote to lower the flag.

Ms Long said the attacks were "madness" and called for the British Government to step in to stop the violence. Speaking to BBC Breakfast, she said: "Last night's attack on two officers guarding my office was a wanton and gratuitous act of attempted murder. There needs to be strong political leadership at this time and not simply left to the police to deal with."

She added: "My heart is breaking for Northern Ireland this morning. We cannot give in to the acts of violence. We owe it to the people of Northern Ireland to keep the peace process intact."

There were also protests on Monday night in Limavady, Co Londonderry, Ballyclare, Co Antrim, Ballycastle, Co Antrim, and Cookstown, Co Tyrone, where the car of a DUP member of the Northern Ireland Assembly, Ian McCrea, was surrounded by angry loyalists.

PSNI Chief Constable Matt Baggott said the some of the violence was intense and there was clearly some paramilitary involvement. It was fortunate no one was seriously injured, he claimed, adding that the situation in some areas was very tense. He said: "There has to be a collective voice to bring this to an end."